The invention relates to a method and an apparatus for the production of a solid-forming or foam-forming mixture composed of at least two flowable reaction components and filler. Two reaction components are injected into a mixing zone under high pressure. The components are mixed with each other and ejected from the mixing zone as a force-fed jet. Filler is added to the jet.
This method may be used in the manufacture of continuous profiles such as webs or foam blocks over prolonged periods during continuous passage through a mixing zone. The method may also be used as a batch process. Mixing takes place during the continuous passage through a mixing zone but the mixing process is interrupted after filling each mold.
The addition of fillers serves various purposes. Inexpensive fillers are added in order to reduce the material costs for articles which will be subjected to only slight stress. Fillers may also be added to achieve specific properties in the resultant products.
The fillers are usually present in finely powdered to granular form. Sometimes they are used in short-fiber form. They are optionally washed. The fillers are generally abrasive and cause marked wear in the feed pipes, the pumps and the injection nozzles.
Attempts have already been made to introduce the fillers directly into the mixhead and mix them with the reaction components. However, sealing problems occurred in this process. Feeding was found to be difficult in high pressure mixheads due to the high conveying pressures needed bacause the fillers clogged the feed pipe.
Therefore, it has also been proposed that the fillers be introduced into the finished reaction mixture by mixing it for a short time with the fillers in an intermediate container. This measure is only practicable with extremely slowly reacting reaction mixtures which makes it undesirable economically.
The object is to find a method enabling fillers to be introduced into a fast reacting reaction mixture. Moreover, it should be possible, if desired, to achieve a maximum filler content in the mixture or in the finished article. The apparatus which can be used should be substantially free from wear. Parts whose wear is unavoidable should be arranged in such a way that they are easily exchangeable. Moreover, sufficiently accurate metering of the fillers should be ensured.